|Designation:||Messier 83, NGC 5236|
|Apparent size:||13.6′ x 13.2′|
|Diameter:||63,000 light years|
|Distance:||16 million light years|
|Exposure:||49 x 179 sec = 2 hrs 46 min|
|Field of View:||37.7 x 37.5 arcmin; Up is 261° E of N|
Visible in both hemispheres – although we get a better view here in the South – M83 is a barred spiral galaxy and one of the brightest in our hemisphere.
In this two and a half hour exposure it displays a bright core and a less well defined bar, from which emerge three clearly defined spiral arms. One is short and two are longer and they contain numerous dark lanes, star fields and nebulosities.
M83 is notable for six supernovae, which were observed between 1923 and 1983.
The Cosmos is all that is or ever was or ever will be.Carl Sagan
I took 62 sub-images of M83 during this session but thirteen were rejected by the brightness filter, so out of 185 minutes of imaging I picked up 146 minutes of data in forty-nine subs:
Nevertheless, almost 2½ hours of exposure was quite satisfying. My friends from Macarthur Astronomical Society who travelled 100 km to a dark sky site that night had to pack up mid-evening due to thick fog, so I was fortunate.
There is still a lot of uncertainty with astronomical distance measurements. For example, statistics in Sky Safari Pro state that M83 is 16 million light years away but in the description on the same page they say 15 million. So I checked around.
Wikipedia says 14.7 million. Wolfram-Alpha puts it at 15.79 million. The Night Sky Observers Handbook (Vol 2) by Kepple and Sanner has it at 22 million. Sometimes doing a bit of research throws up even more confusion!
Simbad includes nine different measurements between 4.47 and 5.16 mega parsecs, which is 14.58 to 16.83 million light years. I give up on researching.
I’m gonna leave it at 16 million …
EDIT (28th June 2020): See comments further below regarding the two faint and tiny galaxies close to M83.
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor.|
|840 mm focal length @ f/7 with field flattener.|
|Baader L-Booster UHC-S light pollution filter 2458276.|
|SkyWatcher EQ6-R Pro mount.|
|Camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx)|
|ZWO ASI120 guide camera, using PHD2 software.|
See annotated image at Astrometry.net